MBP vs MB (External Hard Drive Question)

So I have narrowed it down to the white mid MB, or the lowest end MBP. The last thing I need to understand before making a decision is external hard drive. I read another post about the MBP's PCI slot that you can hook up a SATA hard drive. This sounds nice, but is it that much faster than a 400 firewire of a MB? If I am planning on hooking up external hard drives anyways, should I skip on the 7200 option for the MBP?

I will be using this computer for 3 things. Photoshop for my wife's photography business, video editing for home videos, and audio recording for a personal hobby with cubase.

If there is only a slight difference in external hard drive speeds, I might as well save the money and get the MB, right?

http://www.barefeats.com/hard35.html

This does not show the firewire 400 which would be the only option on a macbook. However, it does compare firewire 800 and sata, which are similar. Hope someone can shed some light, because I am ready to purchase.